This invention relates to an inner mirror of a vehicle and, more particularly, to an inner mirror of a vehicle capable of facilitating watching of visual information in the form of emitted light relating to distance of an obstacle located in the rear of a vehicle.
Various proposals have been made for warning a driver of a vehicle against an obstacle located in the rear of the vehicle when the vehicle is driven rearwardly for, e.g., putting it into a garage. For example, Japanese Patent Application Laid-open No. Sho 59-120877 discloses a device according to which an image in the rear of a vehicle is taken by a television camera and this image is displayed in a CRT provided in a meter panel in front of a driver's seat. Moreover, according to this device, an ultrasonic transmitter and an ultrasonic receiver are provided on a rear bumper to measure distance of an obstacle located in the rear of the vehicle and the measured distance is displayed numerically on the CRT in a form superposed on the image in the rear of the vehicle. This device, however, requires a relatively large scale device such as a television camera and a CRT and therefore is very costly.
For overcoming the problem of this device, Japanese Patent Publication No. Hei 4-25174 proposes an improvement according to which a light emitting device such as a fluorescent character display tube is provided in a part of an inner mirror to display distance of an obstacle located in the rear of a vehicle detected by an obstacle detection sensor. By this arrangement, a driver can watch information relating to the distance of the obstacle located in the rear of the vehicle while he watches an image in the rear of the vehicle over the inner mirror.
According to the device disclosed in Japanese Patent Publication No. Hei 4-25174, the display by the light emitting device is made on a mirror surface and, therefore, distance between a driver's visual point and the display position is smaller than distance between the driver's visual point and an image in the rear of the vehicle reflected by the inner mirror. For this reason, the driver cannot focus his eye both at the display made by the light emitting device and at the image in the rear of the vehicle simultaneously and, accordingly, it is difficult for him to watch the display and the rear image simultaneously. The driver therefore is obliged to watch the display and the rear image alternately but this requires a large amount of shifting of the focus and hence focusing causes fatigue and trouble to the driver.
For overcoming this problem, it is conceivable to provide the light emitting device at a deep position in the mirror body to prolong the distance between the driver's visual point and the light emitting display. This however requires extension of the depth of the mirror body with the result that such a deep mirror body will become an obstacle to driving.
It is, therefore, an object of the invention to provide an inner mirror having a display device which, when information is displayed by light emitting display means provided in the inner mirror, enables an image in the rear of the vehicle and a light emitted display to be watched easily without shifting the driver's focus largely and without enlarging the size of the mirror body.